The present invention concerns a bearing for an open-end spin rotor wherein the shaft of the spin rotor is carried on support disks, wherein a support disk is comprised of a basic body upon which a ringlike, circumferential rim is placed which forms the contact surface for the spin rotor. Common knowledge includes a bearing for an open-end spin rotor wherein a shaft is held by means of supporting disks. In this method, as a rule, two pairs of support disks are installed, in the V-notch between which the shaft of the spin rotor is so placed, that one pair of supporting disks serves as bearings in proximity to the rotor bowl, and the other pair performs a like service on the shaft end remote from said bowl. The surface of the shaft of the open-end spin rotor rotates with practically the same circumferential speed as the support disks. Likewise, the shaft of the open-end spin rotor is a driven shaft, wherein, between the two supporting pairs of disks, a tangential belt is placed which places the said shaft in rotation.
DE 37 34 545 A1 discloses a bearing for an open-end spin rotor. The support disks in this case are furnished with a cooling groove on their bearing contact surfaces, as is also proposed in U.S. Pat. No. 5,178,473 for applications of bearings for open-end spin rotors. A support disk is comprised of a basic body, upon which a contact surface rim is fitted. The said contact surface rim is comprised of plastic, whereby particularly favorable running characteristics are assured for the open-end spin rotor. This rim serves as a damping agent for the spin rotor during its operation as well as assuring a smooth run of the spinning machine. The rolling of the rotor shaft on the rim of a support disk generates heat to the extent that damage can arise. This damage is caused by the overheating of the support disk rims. To alleviate such heating, the U.S. Pat. No. 5,178,473 proposes other particular embodiments of the said rim, such as radiating ribs or a cooling groove in said rim of the supporting disk.
This cooling groove is used practically for all bearing applications for open-end rotor spinning machines, that is applications employing the support disks which are applied there.
DE 195 49 466 shows, in general, how the basic body of a support disk is constructed, so that a favorable connection can be brought about between the plastic rim of the disk and the basic disk body.
U.S. Pat. No. 5,551,226 makes known a support disk for a bearing for an open-end spin rotor, the rim of which is designed with ribbing, so that the rotor shaft rolls on a plurality of individual ribs. The outer side of the ribs, on which the rotor shaft rolls, forms essentially the contact surface for the rotor shaft of the spin rotor. The ribs are at an incline in relation to the middle line M of the rim, so that upon the rolling of the shaft of the spin rotor thereon, an axially acting force is exercised, which in turn braces itself against the reaction of a thrust bearing in the conventional manner.
Indeed, the appearance is given in this version of a support disk bearing that the removal of the heat which arises in the rim during operation of the support disk is excellent in all ways. However, the width of the rim in the area of the contact line with the rotor shaft is so weakened, that an overload of the rim is created. By means of the given conditions involved in a bearing selection for an open-end spin rotor, it is practically not possible to design a support disk wider, simply to compensate for this weakening of the carrying capacity of the support disk. The bearing shown in the U.S. Pat. No. 5,551,226 for an open-end spin rotor is only satisfactory within limits, that is, either the operational speed of rotation of the spin rotor or the tension of the drive belts must be reduced. In practice, such reduction could not be tolerated.
Open-end spinning machines run at the top speed of the open-end spin rotors, whereby rotation speeds of 150,000 RPM's are reached and this value can be considerably overstepped. The environment under which the support disks run is, in fact, very demanding. The processing of cotton, for instance, brings about a high generation of dust which surrounds the open-end spinning machine as well as the bearing for the open-end spin rotor.
This can lead to a state, in which contamination from the environment reacts in such a way with the bearings that during the running of the open-end spin rotor the said contamination accumulates on the shaft of said spin rotor in that area where the shaft contacts the support disks. This contamination is picked up from the ambient surroundings by the support disks and is then redeposited on the surface of the rotor shaft. These deposits can be so solidified that the rotation of the spin rotor can no longer be assured and operational disturbances, such as thread breakage, can come about. Field observations have led to the conclusion that the bearing disk rim, which is comprised of plastic, does not come into contact with the contamination by mechanical contact alone, but under certain circumstances develops an electrostatic charge during the operation and thereby attracts contamination onto its surface, from which this contamination spreads onto the rotor shaft.
The support disks operate between 10,000 and 20,000 RPM so that a high degree of friction develops between the rim and its surrounding air. The electrostatic loading of the rim also causes fines to collect on the surface of the support disk, which comes into contact with the rotor shaft. This contamination, as indicated above, carries over from the surface of the support disk to the rotor shaft, where, because of being subsequently constantly rolled on, the said contamination becomes a solid coating.